A). The specific aims of this proposal are to determine the mechanism(s) of iron acquisition by cardiac cells and the relative turnover rates of significant iron pools within cardiac cells. B). Cardiac cells contain iron-containing proteins, e.g., myoglobin, ferritin, cytochromes. Presumably this iron is supplied from iron-transfer-rin in the blood plasma. Although the transfer of iron from iron-transferrin to erythroid precursors, such as reticulocytes and the lifetime of hemoglobin in erythrocytes have been studied in some detail, the metabolism of iron and iron-containing proteins by cardiac cells appears to be largely unknown. C). By analogy with studies of iron metabolism in erythroid precursors, experiments will be designed to elucidate the mechanism(s) of iron acquisition by cardiac cells and the relative rates of iron-turn-over of certain iron proteins, esp. myoglobin and ferritin within these cells. kinetic studies of the binding and release of radio-labeled transferrin by these cells and of iron transfer from iron-transferrin to these cells will establish the nature of interaction between the iron-carrier protein and these cells. Kinetic studies of radio-iron and radio-labeled amino acid incorporation into myoglobin and ferritin, as well as dual-label "load and chase" studies, will establish the relative synthetic and catabolic rates for these iron proteins. D). This project is intended to establish baseline data for iron metabolism by cardiac cells, which will prove useful in understanding iron-loading by cardiac cells of persons suffering from certain hemolytic anemias, e.g., Cooley's anemia, sickle cell anemia.